Polymer-impregnated carbon fabric is used as an alternative to metallic reinforcement bars in cementitious materials, which is then termed textile-reinforced concrete (TRC). In this study, the bond strength between the cement-based matrix and the fabric was enhanced by decorating the polymer (an epoxy) coating the carbon fabric with hydrophilic micron-size particles (cement or silica) or nanocarbons (functionalized carbon nanotubes or graphene oxide). Cement powder decoration led to a 25% increase in the bond strength (measured by a pull-off test) and a 30% improvement in the mechanical properties of the composite. At the micron scale, the decoration resulted in the formation of a 100-μm thick interlayer between the decorated fabric and the cement-based matrix. Unexpectedly, exposure of the cement-decorated samples to a NaCl environment (as in off-shore constructions) resulted in enhanced bond strength due to the growth of salt crystals at the fabric–matrix interface.
The determination of food freshness along manufacturer-to-consumer transportation lines is a challenging problem that calls for cheap, simple, reliable, and nontoxic sensors inside food packaging. We present a novel approach for oxygen sensing in which the exposure time to oxygen—rather than the oxygen concentration per se—is monitored. We developed a nontoxic hybrid composite-based sensor consisting of graphite powder (conductive filler), clay (viscosity control filler) and linseed oil (the matrix). Upon exposure to oxygen, the insulating linseed oil is oxidized, leading to polymerization and shrinkage of the matrix and hence to an increase in the concentration of the electrically conductive graphite powder up to percolation, which serves as an indicator of food spoilage. In the developed sensor, the exposure time to oxygen (days to weeks) is obtained by measuring the electrical conductivity though the sensor. The sensor functionality could be tuned by changing the oil viscosity, the aspect ratio of the conductive filler, and/or the concentration of the clay, thereby adapting the sensor to monitoring the quality of food products with different sensitivities to oxygen exposure time (e.g., fish vs grain).
h i g h l i g h t sCarbon allotropes of various dimensionalities are explored in reinforcing cement. Effect of nanofillers on fresh and hardened states of cement composites is investigated. Compatibility and dimensionality of nanofillers play a crucial role in reinforcing cement composites.
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